Population

Population

FAO worldwide reported landings show a steady increase from 103,676 t in 1950 to 284,542 t in 2006 (FAO 2009). There are six stocks that are globally managed for this species. As of 2004, the stock in the North Atlantic is considered Overexploited; the Indian Ocean and North Pacific are Fully Exploited; the South Atlantic and South Pacific are Moderately Exploited; and the Mediterranean is Unknown (Majkowski 2007). Populations in the Eastern Pacific consist of the South Pacific stock and the North Pacific stock. Details of the migration remain unclear, but juvenile fish (2–5 years) are believed to move into the eastern Pacific Ocean in the spring and early summer, and return to the western and central Pacific, perhaps annually, in the late fall and winter, where they tend to remain as they mature (IATTC 2008). Recent estimates of total catch data from IATTC (2008) for the Eastern Pacific are 24,604 mt (2005), 30,393 mt (2006), and 8,587 mt (2007).

North Pacific OceanAn assessment for the North Pacific stock conducted in 2006 (Stocker 2006, ISC 2008) found that spawning stock biomass (SSB) has experienced slight fluctuations since 1960s, but has remained relatively stable at ~90,000 mt over the last two decades. Linear regression of SSB over the past 20 years (1987–2005), shows only a very small decline of approximately 6%. The total catch increased substantially in 2007, to a level typical of the catches occurring during the 1996–2004 period, while preliminary catch for 2008 decreased to a level more consistent with catches after 2004. Even though current fishing mortality is projected to be above FMSY, recent changes in the distribution of the fishery need to be appropriately standardized before relative abundance can be accurately reflected (Holmes 2009). A new stock assessment planned for 2011.

South Pacific OceanBased on Multifan-CL stock assessment conducted in 2008 (Hoyle et al. 2008), SSB has decreased approximately 36–40% over the past 20 years (1987–2007). However, the conclusion is that this species is not in an overfished state, with current catch levels being sustainable (Hoyle and Davies 2009). Although estimates are highly variable between model configurations, 2004–2006 mortality is estimated to be below FMSY, and 2004–2006 biomass is estimated to be above BMSY, and spawning stock biomass between 2004–2006 is estimated to be above SSBMSY (Hoyle and Davies 2009).

Indian OceanThe only stock assessment available for this species in the Indian Ocean, conducted in 2008, may be unreliable (Hilary 2008). In terms of predicted stock-status, the model predicted that the stock biomass in the Indian Ocean was very close to MSY but that the current harvest rate was above the MSY level indicating that over-fishing may be occurring. The 2007 catch level (31,226 tonnes) was predicted to be above the MSY level (27,022 tonnes) with high probability. This assessment is very preliminary and it should be recommended that a more realistic fully age/length structured model be developed for the future to assess this stock (Hilary 2008).

Based on this exploratory stock assessment, estimated SSB in the Indian Ocean has declined approximately 55% over the past 20 years (1987–2007), even though in the past four years (2002–2006) estimated SSB has increased from 20,000 to 40,000 tonnes. Standardized CPUE has also declined over the past 25 years, but has been relatively stable since 1990 (IOTC 2008). Current mortality is below FMSY. Although results of these analyses are considered preliminary and indicative only, it was concluded that this stock is not presently overfished (IOTC 2008).

North Atlantic OceanCatches of this species in the north Atlantic peaked at 65,000 tonnes in the mid-1960s, then declined to a low of 20,000 tonnes in 2008. This decline is partly due to reduced fishing effort by some surface and longline fisheries. The most recent stock assessment in 2009 indicated that recruitment in the fishery is highly variable, and that biomass since 1993 has been less than biomass at MSY. Currently, the stock is about 40% below the MSY level and spawning stock biomass is currently only 25% of the original biomass (ICCAT 2009). The MSY from the last stock assessment was estimated at 29,000 tonnes, and catches in four of the last ten years have exceeded this value. This species stock in the North Atlantic was recently considered to be in an overfished state (ISSF 2010, Joseph 2009). However, in 2009 catch quotas were adopted in line with scientific advice to end overfishing.

In the 2009 stock assessment for the north Atlantic (ICCAT 2009), several models were used to evaluated the status of the stock. Based on linear regression of the Multifan base case, estimated spawning stock biomass has decreased approximately 33% over the past 20 years (1987–2007).

South Atlantic OceanIn the South Atlantic, catches have varied from a high of 41,000 tonnes in 1987 to a low of 15,000 tonnes in 1984. Catches were stable from 1988 to 2001 at ca. 30,000 tonnes, and the average in the last five years has been 21,000 tonnes (ISSF 2010). The current estimate of MSY is 33,000 tonnes, ranging between 29,000 and 36,700 tonnes. In the last ten years only one year had a catch exceeding the MSY estimate. It is likely that the stock is below the maximum sustainable yield (MSY) level as it was estimated to about 90% of BMSY in 2005, while the 2005 fishing mortality rate was about 60% of FMSY (SCRS ICCAT 2010). The stock is considered to be in a slightly overfished state, but is not currently being fished above MSY (ISSF 2010).

In the 2007 stock assessment for the South Atlantic (ICCAT 2007), several models were used to evaluated the status of the stock. Based on linear regression of the ASPM age structured production model base case, estimated SSB has decreased approximately 32% over the past 20 years (1987–2007).

MediterraneanA stock assessment for the Mediterranean is planned for 2011. The Mediterranean albacore fisheries are characterized by high spatio-temporal variability in landings and fishing patterns. Albacore fishing is a traditional activity for a number of fleets including those of Cyprus, Greece, Italy, Spain, and Malta. ICCAT statistics, however, are considered quite incomplete due to unreported catches from several countries and the lack of data in some years from other countries. Fishing effort is not possible to estimate due to short time series and inadequate coverage of artisanal gears. Even though catches of Mediterranean albacore have been increasing for the past few years, there is a lack of general information on this stock and biological information is also limited (ICCAT 2010). Although many countries are not yet reporting any catch for this species, the Mediterranean stock does not show any general trend, and the mixing rate with the Atlantic stock appears to be insignificant (STECF 2007).